Need some tips on how flex 4.6 works in great lines.

Hello, It has been some years ago when I worked with flex.

I just started with flex 4.6 for mobile. I did some testing but could not really undertand the spark
components

For example if you have a spark label and apply some text to it, you don't know the new label height as
I traced out it's alway 0. Only when it's added to the stage you can trace it's height.

All components seem to work differently with setting the width and height as I was used to Flex.

Does this mean I have to add all elements
I need first to the stage and then when loading external text reposition everything? I tried that, but then you see
the first time a split second a strange layout and then it gets resized and repositioned.

Does anyone have short description on how it supposed to work?

Regards,
Chris.